CN112994759B - Cooperative relay D2D communication method based on OFDM - Google Patents

Abstract

The invention discloses a cooperative relay D2D communication method based on OFDM, which comprises the steps that a remote D2D pair carries out data relay communication through a special D2D pair, the special D2D pair multiplexes a plurality of resources and serves as relay equipment, and a plurality of available resources are utilized to carry out signal transmission based on OFDM; the frame structure of the communication system is divided into two time slots with equal length, the special D2D transmitter can send signals and receive relay forwarding signals in odd time slots, and the special D2D transmitter sends self transmission signals and forwards relay forwarding signals based on OFDM in even time slots. According to the invention, the D2D user is selected as the relay equipment of the remote D2D pair, so that the problem that D2D communication cannot be carried out due to distance limitation can be effectively solved, and the D2D access quantity of the system is effectively increased; the condition that one D2D multiplexes a plurality of cellular resources can be fully utilized through the OFDM technology, the utilization efficiency of the spectrum in the system is effectively improved on the premise of ensuring the special D2D communication quality serving as a relay, and the method has wide practical value and application prospect.

Description

A Cooperative Relay D2D Communication Method Based on OFDM

technical field

The present invention relates to wireless communication, in particular to an OFDM-based cooperative relay D2D communication method.

Background technique

With the rapid development of information technology and the explosive growth of the number of multimedia smart devices, as well as the online use of various multimedia applications, and with the high requirements for communication service quality, delay and speed, existing communication means and communication resources It is difficult to respond to and provide the real needs of users. As one of the technical components of the 5G architecture, D2D communication is a communication mode that does not require data forwarding through the base station, and can directly transmit data between neighboring devices. As shown in Figure 1, D2D users can directly perform short-distance communication by multiplexing cellular user resources, which can greatly reduce the number of data processing and forwarding at the base station, greatly improve the utilization of spectrum resources, and further improve the total throughput of the system and expand Network capacity, reduce power consumption and guarantee Qos for user communication.

The communication frequency band used by D2D is a telecom authorized frequency band, and the base station can control the user's transmission power, mode selection and resource multiplexing. The resource used by the D2D communication may be the communication resource of the shared cellular user or occupy a communication channel independently. In general, there are three communication modes for D2D pairs: dedicated mode, cellular mode, and shared mode (multiplexing mode), but the shared mode is the most commonly used one. The shared mode can greatly improve spectrum utilization efficiency and cell communication. capacity.

In the multiplexing mode, multiplexing resources can be divided into one-to-one multiplexing mode and many-to-one multiplexing mode. As shown in FIG. 2 , in the figure, the D2D users all adopt the multiplexing mode, the D2D_1 user multiplexes the resource of the cellular user CUE_1 , and the D2D_2 and D2D_3 jointly multiplex the resource of the cellular user CUE_2 . Compared with the one-to-one multiplexing mode, the many-to-one multiplexing mode can enable the system to accommodate more communication users and further improve the spectrum utilization rate of the system. In the many-to-one resource multiplexing mode, D2D users can perform resource multiplexing by grouping, and grouping can control the interference between D2D users in the group to be as small as possible. During the grouping process, some D2D pairs can perform resource multiplexing in multiple cellular user resource blocks, but in the actual multiplexing process, one D2D traffic can multiplex one resource block to complete the communication task, resulting in waste of spectrum in the system. D2D communication can reduce the load of the base station due to its short-distance direct connection communication, but when the distance between the devices is relatively large, the communication quality of the two devices cannot be guaranteed or even the connection may not be possible. In this case, when there are available resources, it will It will affect the communication performance of the whole system.

Contents of the invention

Purpose of the invention: The purpose of the present invention is to solve the problem of D2D users being unable to communicate directly due to the long distance and the problem of frequency waste, and to provide an OFDM-based cooperative relay D2D communication method, which can increase the number of D2D accesses in the system while also increasing the number of D2D users. Guarantee the communication quality of special D2D users.

Technical solution: An OFDM-based cooperative relay D2D communication method, the long-distance D2D pair performs data relay communication through a special D2D pair, and the special D2D pair multiplexes multiple resources and acts as a relay device, utilizing multiple available resources based on OFDM Carry out signal transmission; divide the frame structure of the communication system into two time slots of equal length. In odd time slots, the special D2D transmitter can both send signals and receive relay forwarding signals. In even time slots, the special D2D transmitter is based on OFDM sends its own transmit signal and repeat-repeat-repeat signal.

Furthermore, cellular users normally communicate with the base station BS using the uplink in all time slots, ordinary direct-connected D2D users normally multiplex cellular resources for communication in all time slots, long-distance D2D transmitters send signals in odd time slots, and transmit signals in even-numbered time slots. Time slots receive relay forwarding signals; special D2D pairs acting as relays use a cellular resource for normal direct communication in odd time slots, use other available multiplexed resources to receive relay forwarding signals, and send their own communication signals in even time slots and relay forwarding signals.

Further, the long-distance D2D transmitter sends information to the special D2D transmitter acting as a relay by multiplexing the pairable cellular resources of the special D2D pair in odd time slots.

Further, the special D2D transmitter acting as a relay uses two cellular resources at the same time in odd time slots, communicates normally on one resource, does not send signals on the other resource, and only receives signals from remote D2D users and performs Stored for forwarding in even time slots.

Further, the special D2D transmitter acting as a relay simultaneously multiplexes two resource blocks that can be paired based on OFDM to transmit signals in even time slots, and sends signals to the long-distance D2D receiver and the special D2D receiver based on OFDM respectively.

Further, the long-distance D2D receiver and the special D2D receiver receive signals sent from the special D2D transmitter acting as a relay in even time slots.

Beneficial effects: Compared with the prior art, the present invention has the following significant advantages: by selecting a D2D user as the relay device of a long-distance D2D pair, it can effectively solve the problem that D2D communication cannot be performed due to distance limitation, and effectively improve The number of D2D accesses in the system; OFDM technology can make full use of the multiplexing of multiple cellular resources in one D2D, and effectively improve the spectrum utilization efficiency in the system on the premise of ensuring the quality of special D2D communication acting as a relay.

Description of drawings

FIG. 1 is a D2D communication link diagram under the LTE system;

Figure 2 is a scene diagram of one-to-one and many-to-one resource reuse;

FIG. 3 is a diagram of a D2D communication scenario in which a D2D user acts as a relay in the present invention;

Fig. 4 is a schematic diagram of the system information transmission scheduling frame structure in the present invention;

FIG. 5 is a scene diagram of OFDM-based cooperative relay D2D communication in the present invention;

FIG. 6 is a general model diagram of an OFDM-based cooperative relay D2D communication scenario in the present invention.

detailed description

The specific implementation manners of the present invention will be further described in detail below in conjunction with the drawings and examples.

As shown in Figure 3, the D2D pair device is used as a relay device, and the D2D pair acting as a relay is called a special D2D pair, which can effectively use the spectrum resources in the system and increase the number of D2D communications that the system can access.

Divide the system frame structure into two time slots with alternating odd and even times and the same length. Cellular users normally communicate with the base station BS using the uplink in all time slots. Ordinary direct-connected D2D users normally multiplex cellular resources for communication in all time slots. The long-distance D2D transmitter sends signals in odd-numbered time slots, and the long-distance D2D receiver receives relayed signals in even-numbered time slots. A special D2D user acting as a relay uses a cellular resource for normal direct-connection communication in odd time slots, uses another available multiplexed resource to receive relay forwarding signals, and transmits its own communication signals and relay forwarding signals in even time slots. As shown in Figure 4.

As shown in Figure 5, the OFDM-based cooperative relay D2D communication transmission scheme proposed by the present invention is aimed at a single cell communication scenario. There are multiple cellular users and D2D users in the cell. Then resource multiplexing is carried out. When D2D pairs are grouped, a D2D pair can be paired with multiple cellular resources. However, in actual use, it is stipulated that a D2D pair can only reuse one cellular resource. In order to improve spectrum utilization, it is proposed OFDM-based cooperative relay for D2D communication. As shown in Figure 6, the analysis is carried out for a cooperative relay transmission situation. The cell contains a base station, a pair of long-distance D2D pairs, and two D2D groups. These two groups can be used as a special D2D pair (D2D_1 ) for multiplexing. Long-distance D2D cannot communicate normally due to distance limitations. The special D2D transmitter acting as a relay receives the signal sent by the long-distance D2D transmitter and forwards it to the long-distance D2D receiver. At the same time, the special D2D pair can also communicate normally. The dotted line in the figure represents the interference signal. The process of this solution will be described below by taking the data transmission of the system in two time slots as an example.

(1) Odd time slots

Step 1: The long-distance D2D transmitter sends information to the special D2D transmitter acting as a relay by multiplexing special D2D pairable cellular resources in odd time slots. As shown in Figure 6, the special D2D pair can multiplex the cellular resources of group 1 and group 2 at the same time, and the long-distance D2D transmitter can arbitrarily multiplex one of the resources for data transmission S ₀ , and the special D2D user can multiplex the remaining one resource for normal The signal transmission S ₁ .

Step 2: The special D2D transmitter does not transmit signals in odd time slots and long-distance multiplexing with the same resource, but only receives and stores signals from remote D2D users for forwarding in even time slots. The special D2D transmitter receives the signal S ₀ sent by the long-distance D2D transmitter, and also receives the signals sent by other D2D transmitters in the cluster. Except for the S ₀ signal, other signals are interference signals.

(2) Even time slots

Step 4: The special D2D transmitter acting as a relay in even time slots multiplexes two resource blocks that can be paired simultaneously to send signals through OFDM technology. The signals S ₂ and S ₃ are respectively sent to the long-distance D2D receiver and the special D2D receiver through OFDM technology. Through OFDM technology, a special D2D transmitter can use the cellular resources of group 1 and group 2 at the same time, and use orthogonal resources to send signals S ₂ and S ₃ to two receivers without interfering with each other.

Step 5: The long-distance D2D receiver and the special D2D receiver receive the signal sent from the special D2D transmitter acting as a relay in even time slots. The long-distance D2D receiver and the special D2D receiver receive the useful signals S ₂ and S ₃ and also receive the communication signals of other D2D users (D2D_2 and D2D_3) in the group, and these signals can be regarded as interference signals for correct signal reception.

All descriptions that are not involved in the specific embodiments of the present invention belong to the known technology in the art and can be implemented with reference to the known technology. The present invention is verified through repeated experiments, and relatively satisfactory effects have been obtained.

Claims (6)

1. A cooperative relay D2D communication method based on OFDM, characterized in that a long-distance D2D pair performs data relay communication through a special D2D pair, the long-distance D2D pair includes a long-distance D2D transmitter and a long-distance D2D receiver, the special D2D pair includes a special D2D transmitter and a special D2D receiver, the special D2D pair multiplexes a plurality of resources and serves as a relay device, and performs signal transmission using a plurality of available resources based on OFDM; a frame structure of a communication system is divided into two time slots with equal length, a special D2D transmitter can send signals and receive relay forwarding signals in odd time slots, and the special D2D transmitter sends self transmission signals and forwards the relay forwarding signals based on OFDM in even time slots.

2. The OFDM-based cooperative relay D2D communication method according to claim 1, wherein cellular users normally communicate with a base station BS using an uplink in all time slots, normal direct-connected D2D users normally multiplex cellular resource communication in all time slots, a long-distance D2D transmitter transmits signals in odd time slots, and a long-distance D2D receiver receives the relay forwarding signals in even time slots; the special D2D pair serving as the relay performs normal direct connection communication by using one cellular resource in the odd time slot, receives the relay forwarding signal by using another available multiplexing resource, and transmits a self communication signal and the relay forwarding signal in the even time slot.

3. The OFDM-based cooperative relaying D2D communication method according to claim 2, wherein the long-range D2D transmitter transmits information to the special D2D transmitter acting as a relay by multiplexing the special D2D pair pairable cellular resources at the odd slots.

4. The method of claim 3, wherein the special D2D transmitter acting as a relay uses two cellular resources simultaneously in the odd slots, communicates normally on one resource, does not transmit on the other resource, receives only signals from far-end D2D users and stores them for retransmission in the even slots.

5. The OFDM based cooperative relay D2D communication method according to claim 4, wherein the special D2D transmitter acting as a relay simultaneously multiplexes two resource blocks that can be paired for signal transmission based on OFDM in the even slots, and respectively transmits signals to the long-distance D2D receiver and the special D2D receiver based on OFDM.

6. The OFDM based cooperative relaying D2D communication method as claimed in claim 5, wherein the long range D2D receiver and the special D2D receiver receive the signal transmitted from the special D2D transmitter acting as a relay at the even numbered slots.

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